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class="fa fa-bars"></i> <a href="../index.html">ServiceComb Java Chassis 开发指南</a> </nav> <div class="wy-nav-content"> <div class="rst-content"><div role="navigation" aria-label="breadcrumbs navigation"> <ul class="wy-breadcrumbs"> <li><a href="../index.html" class="icon icon-home" alt="Docs"></a> &raquo;</li> <li>文件下载开发指导</li> <li class="wy-breadcrumbs-aside"> </li> </ul> <hr/> </div> <div role="main" class="document" itemscope="itemscope" itemtype="http://schema.org/Article"> <div class="section" itemprop="articleBody"> <h1 id="_1">文件下载开发指导</h1> <h2 id="_2">服务提供者开发</h2> <p>文件下载支持采用 Spring MVC 和 Jax RS 开发。 因为文件下载都是 GET 方法， 因此两者的使用差异很小， 这里的例子只提供 Spring MVC 。 </p> <ul> <li>File</li> </ul> <p>最简单的例子，接口的返回参数声明为 File 类型的参数， 即可定义一个下载接口。 </p> <pre><code>@GetMapping(path = &quot;/file&quot;) public File file(String name) </code></pre> <ul> <li>Part</li> </ul> <p>如果需要根据请求参数动态创建临时文件，下载完成后，将临时文件删除，可以采用 Part 类型的参数。</p> <pre><code>@GetMapping(path = &quot;/file&quot;) public Part file(String content) throws IOException { File file = createTempFile(content); return new FilePart(null, file) .setDeleteAfterFinished(true) .setSubmittedFileName(&quot;test.txt&quot;); } </code></pre> <ul> <li>Resource</li> </ul> <p>可以将接口声明为 org.springframework.core.io.Resource。 由于resource不一定表示文件下载，所以需要通过 @ApiResponse 标识这是一个文件下载场景</p> <p>以ByteArrayResource为例说明：</p> <pre><code>@GetMapping(path = &quot;/resource&quot;) @ApiResponses({ @ApiResponse(code = 200, response = File.class, message = &quot;&quot;) }) public Resource resource() { return new ByteArrayResource(bytes) { @Override public String getFilename() { return &quot;resource.txt&quot;; } }; } </code></pre> <p>上例中，因为ByteArrayResource没有文件名的概念，所以需要实现Resource的getFilename方法，也可以通过ResponseEntity 进行包装：</p> <pre><code>@GetMapping(path = &quot;/resource&quot;) @ApiResponses({ @ApiResponse(code = 200, response = File.class, message = &quot;&quot;) }) public ResponseEntity&lt;Resource&gt; resource() { return ResponseEntity .ok() .header(HttpHeaders.CONTENT_TYPE, MediaType.TEXT_PLAIN_VALUE) .header(HttpHeaders.CONTENT_DISPOSITION, &quot;attachment;filename=resource.txt&quot;) .body(resource); } </code></pre> <ul> <li>InputStream</li> </ul> <p>一样的， 使用 InputStream 需要 @ApiResponse 标识这是一个文件下载场景</p> <pre><code>@GetMapping(path = &quot;/inputStream&quot;) @ApiResponses({ @ApiResponse(code = 200, response = File.class, message = &quot;&quot;), }) public ResponseEntity&lt;InputStream&gt; download() throws IOException { return ResponseEntity .ok() .header(HttpHeaders.CONTENT_TYPE, MediaType.TEXT_PLAIN_VALUE) .header(HttpHeaders.CONTENT_DISPOSITION, &quot;attachment;filename=resource.txt&quot;) .body(stream); } </code></pre> <p>在下载完成后，ServiceComb会自动关闭stream，开发人员不必再关注。</p> <ul> <li>文件类型判定</li> </ul> <p>只要没有通过ResponseEntity直接设置HttpHeaders.CONTENT_TYPE，ServiceComb都会尝试通过File、Part、Resource中的文件名后缀进行自动判定。</p> <p>ServiceComb使用java的mime type机制进行文件类型判定，如果业务场景中的文件后缀无法被识别，ServiceComb会默认处理为application/octet-stream</p> <p>如果这不满足要求，假设文件后缀为xyz，期望文件类型为application/file-xyz，以下方式任选一种均可解决：</p> <ol> <li>通过Java的mime type机制扩展</li> </ol> <p>在META-INF目录下，创建mime.types文件，其内容为：</p> <pre><code>application/file-xyz xyz </code></pre> <pre><code>2. 在业务代码中通过Part指定 </code></pre> <pre><code>@GetMapping(path = &quot;/tempFilePart&quot;) public Part tempFilePart(String content) throws IOException { File file = createTempFile(content); return new FilePart(null, file) .setDeleteAfterFinished(true) .contentType(&quot;application/file-xyz&quot;) .setSubmittedFileName(&quot;tempFilePart.txt&quot;); } </code></pre> <pre><code>3. 在业务代码中通过ResponseEntity指定 </code></pre> <pre><code>@GetMapping(path = &quot;/tempFileEntity&quot;) public ResponseEntity&lt;Part&gt; tempFileEntity(String content) throws IOException { File file = createTempFile(content); return ResponseEntity .ok() .header(HttpHeaders.CONTENT_TYPE, &quot;application/file-xyz&quot;) .header(HttpHeaders.CONTENT_DISPOSITION, &quot;attachment;filename=tempFileEntity.txt&quot;) .body(new FilePart(null, file) .setDeleteAfterFinished(true)); } </code></pre> <ul> <li>指定文件名</li> </ul> <p>只要没有通过ResponseEntity直接设置HttpHeaders.CONTENT_DISPOSITION，ServiceComb都会尝试通过File、Part、Resource中的文件名生成HttpHeaders.CONTENT_DISPOSITION，假设文件名为file.txt，则生成的数据如下：</p> <pre><code>Content-Disposition: attachment;filename=file.txt;filename*=utf-8’’file.txt </code></pre> <p>不仅仅生成filename，还生成了filename*，这是因为如果文件名中出现了中文、空格，并且filename正确地做了encode，ie、chrome都没有问题，但是firefox直接将encode后的串当作文件名直接使用了。firefox按照<a href="https://tools.ietf.org/html/rtf6266">https://tools.ietf.org/html/rtf6266</a>，只对filename*进行解码。</p> <p>如果业务代码中直接设置Content-Disposition，需要自行处理多浏览器支持的问题。</p> <p>文件下载的更多用法可以通过下载 java-chassis 源码， 查看 DownloadSchema 里面的例子。</p> <h2 id="_3">服务消费者开发</h2> <p>消费者统一使用 org.apache.servicecomb.foundation.vertx.http.ReadStreamPart 处理文件下载。 可以使用透明 RPC 方式， </p> <pre><code>public interface ……{ ReadStreamPart download1(……); ReadStreamPart download2(……); } </code></pre> <p>或者 RestTemplate</p> <pre><code>ReadStreamPart part = restTemplate.getForObject(url, ReadStreamPart.class); </code></pre> <p>ReadStreamPart提供了一系列方法，将数据流保存为本地数据：</p> <pre><code>org.apache.servicecomb.foundation.vertx.http.ReadStreamPart.saveAsBytes() org.apache.servicecomb.foundation.vertx.http.ReadStreamPart.saveAsString() org.apache.servicecomb.foundation.vertx.http.ReadStreamPart.saveToFile(String) org.apache.servicecomb.foundation.vertx.http.ReadStreamPart.saveToFile(File, OpenOptions) </code></pre> <p><strong><em>注意：</em></strong></p> <ul> <li>在得到ReadStreamPart实例时，并没有完成文件内容的下载，调用save系列方法才开始真正从网络上读取文件数据。</li> <li>如果使用saveAsBytes、saveAsString，数据是直接保存在内存中的，如果下载的文件很大，会导致内存溢出。</li> <li>save系列方法，返回的都是CompletableFuture对象， 如果要阻塞等待下载完成，通过future.get()即可； 如果通过future.whenComplete进行异步回调处理，要注意回调是发生在网络线程中的，此时需要遵守reactive的线程规则。</li> </ul> </div> </div><footer> <hr/> <div role="contentinfo"> <!-- Copyright etc --> </div> Built with <a href="https://www.mkdocs.org/">MkDocs</a> using 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